The disease characteristics are accurately studied and judged through refined detection on site aiming at such composite diseases as sedimentation, leakage and structural aging that have become prominent during the operations of closed conduit for diversion closed conduit of Baotou Steel for over 65 years. The systematic comprehensive treatment scheme is established by adopting the collaborative dredging technology of “horizontal directional drilling machine+ dredging vehicle with high-pressure water jet” and graded leaking stoppage technology of composite grouting as well as combining with the full-process closed-loop construction monitoring system. The water transfer function of closed conduit is fully recovered, conveyance capacity is increased from 30% before treatment to 5 m³/s, the designed flow rate of water transfer and service life of structure is extended by over 15 years after implementing this scheme, which provides the reproducible and propagable technological paradigm for treating aged water conservancy facilities in the Yellow River basin.